There are many different type of bottle closures or bottle end caps known in the prior art for closing and sealing the open ends of bottles and the like. Moreover, many such prior art bottle caps include resilient seals or gaskets for insuring a leak-tight seal with the bottle. However, bottles frequently have irregularly shaped end surfaces, and prior art bottle caps are not always effective to achieve a secure, leak-tight seal with such irregularly shaped bottle end surfaces. This is particularly true when relatively hard materials are used for the bottle end cap, such as Teflon and the like. There has been a recent increase in demand for bottle end caps made of Teflon because of the inherent properties of Teflon, and accordingly, some means is necessary in order to insure that Teflon bottle caps will achieve a leak-tight seal with irregularly shaped bottle end surfaces.
In accordance with the present invention, a resilient insert is provided between a relatively thin, yieldable end closure of the cap, and a relatively thick back-up flange is spaced from the end closure, with the insert provided between the flange and end closure, such that when the bottle cap is tightened on the end of a bottle and the like, the end closure and resilient insert are resiliently yieldable to enable the bottle cap to effect a secure and leak-tight seal with the bottle end surface.